CMP is a common method to planarize substrates. CMP utilizes a slurry generally including water, an oxidizer and particles for selective removal of material from substrates. In conventional CMP, a substrate carrier or polishing head is mounted on a carrier assembly and positioned in contact with a polishing pad in a CMP apparatus. The carrier assembly provides a controllable pressure to the substrate pressing the substrate against the polishing pad. The pad is moved relative to the substrate.
Hard slurry particles such as diamond, cubic boron nitride, silicon carbide, and boron carbide, are routinely applied to polish hard substrates using a mechanical polishing process such as lapping and grinding. The size of the particles typically controls the polishing rate, where the larger the particle size the higher the polishing rate. However, larger particles also cause higher surface and sub-surface damage, so that mechanical polishing processes may employ multiple steps. For example, initially larger sized particles can be used in earlier CMP step(s) followed by smaller and smaller size particles in later CMP step(s) in an attempt to improve the removal rate and the surface finish. Typically such large hard particles are not used in CMP processes as they can induce a high degree of damage during the polishing processes.